Titanic Urn of Souls

Titanic Urn of Souls Power and Toughness are
equal to the number of permanents in
your graveyard.
At the beginning of your upkeep, Choose One:
-Mill 4 cards
-Return any number of creatures from your graveyard to the battlefield, exile your graveyard.
The souls of the dead that clung to the urn eagerly
await its destruction, so that they may roam
free once more.